HUALIEN: Grieving relatives of those who died in Taiwan's worst rail disaster in decades held prayers at the crash site on Saturday as salvage crews worked to remove the tangled mass of wrecked carriages.

Officials said Friday's devastating collision, which killed at least 51 people and injured nearly 190, was caused when a parked railway maintenance vehicle slipped down an embankment and onto the tracks.

A train packed with as many as 500 people at the start of a long holiday weekend then hit the truck just as it entered a narrow tunnel near the eastern coastal city of Hualien. The truck driver -- who railway officials said may have failed to secure the parking brake properly -- has been released on bail after being interrogated by prosecutors and is barred from leaving Taiwan pending further investigation.

Around one hundred relatives held an emotional Taoist prayer ceremony near the crash site on Saturday afternoon, shaded under a canopy of black umbrellas.

Many wept openly as they surveyed the scene, some holding makeshift shrines inscribed with the names of those who died.

Some called out the names of their loved ones as other family members held them tight. Rescuers described an appalling scene as they rushed into the tunnel and found the front of the train pulverised into a twisted mesh of metal.